Your NAP180 is the epitome of a classic Naim amplifier, where the necessary inductance for amp stability is provided by the speaker cable (thus extra inductance in the amp itself is not necessary giving better performance). Therefore it requires at least 3.5m per channel of low capacitance and moderately high inductance speaker cable (ideally NACA5 or else similar figure-8 multi-strand copper cable). You should definitely steer well clear of any litz, heavily twisted or woven type of cable as this usually lowers inductance and increases capacitance which could well cause instability in the amp.
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